Marine Weather Net

Straits of Florida from west end of Seven Mile Bridge to south of Halfmoon Shoal out 20 to 60 NM Marine Forecast


5 - 10




The Marine Weather Forecast In Detail:
GMZ074 Forecast Issued: 444 AM EST Mon Jan 20 2020

Today...Variable Winds 5 To 10 Knots, Becoming North And Increasing To Near 15 Knots. Seas 2 To 3 Feet, Building To 3 To 5. Scattered Showers.
Tonight...North Winds Increasing To Near 20 Knots. Seas 4 To 7 Feet. Isolated Showers.
Tuesday...Northwest To North Winds Decreasing To 15 To 20 Knots. Seas 4 To 7 Feet. Isolated Showers.
Tuesday Night...North Winds Increasing To 20 To 25 Knots. Seas 5 To 9 Feet.
Wednesday...North Winds 20 To 25 Knots, Decreasing To Near 15 Knots. Seas 5 To 9 Feet. Isolated Showers.
Wednesday Night...Northeast To East Winds 15 To 20 Knots. Seas 5 To 8 Feet. Isolated Showers.
Thursday...East Winds 15 To 20 Knots. Seas 4 To 7 Feet. Isolated Showers.
Thursday Night...East To Southeast Winds 15 To 20 Knots. Seas 4 To 6 Feet. Scattered Showers.
Friday...Southeast Winds 10 To 15 Knots. Seas 2 To 4 Feet. Scattered Showers.
Friday Night...South To Southwest Winds Near 10 Knots. Seas 2 To 3 Feet. Isolated Showers.
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Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005
444 AM EST Mon Jan 20 2020

A strong cold front will drive through the Florida Keys, moving from Dry Tortugas Monday morning through the Straits of Florida offshore the Upper Keys by mid to late this afternoon. Strong northerly breezes will become established this evening and continue into Wednesday. High pressure building southeast down the eastern U.S. will turn gentle winds easterly by the end of the week.

Gulf Stream
The Approximate Shoreward Edge of the Gulf Stream as of January 20...
- 9 NM South of Dry Tortugas Light...on Loggerhead Key.
- 2 NM South of Cosgrove Shoal the Marquesas Keys. Less than
- 1 NM South of Sand Key Key West.
- 2 NM South of Looe Big Pine Key.
- 3 NM South of Sombrero Key Marathon.
- 2 NM Southeast of Alligator Reef Islamorada. Less than
- 1 NM Southeast of Molasses Reef Key Largo. Less than
- 1 NM East of Carysfort Reef Ocean Reef.
Area Forecast Discussion
National Weather Service Key West FL
508am EST Monday Jan 20 2020

Currently - A strong cold front is racing southward into the southeastern Gulf of Mexico early this morning. The Keys, being ahead of the front, are in a baggy pressure field and weak variable winds. There is some confluence being generated across the Florida Straits due to predominantly northerly flow to our northwest and southerly flow to the southeast. As a result, a few broken bands of showers have developed. Temperatures are around 70 degrees with dew points only a degree or two below that producing damp conditions.

Short Term Update
A sprawling high pressure descending down the plains will drive the cold front through the Keys today. Expect winds to strengthen today into tonight. Rain chances will decrease gradually through the day as steadily drier air arrives behind the cold front. This front will be accompanied by one of the more significant cool air pushes thus far this winter and temperatures are expected to push down towards 60 degrees tonight with dew point temperatures falling towards 50.

Portions of the Keys will lull a little tomorrow as the mainland gets some sun. However, the background flow will gradually strengthen as the high builds into the eastern United States. Meanwhile, strong jet dynamics and warm gulf stream waters will produce falling pressures off the southeastern United States coast. This will help tighten the local pressure gradient and to pin our winds northerly. The continued cool flow will keep highs near 70 with dew points falling further into 40s. The strongest winds will arrive tomorrow night due to the arrival of the coolest air, the strongest pressure gradient, and mainland cooling. Winds will be quite windy by Wednesday morning, with temperatures diving further into the lower 50s and dew points nosing near 40.

Winds will diminish on Wednesday as the high cell moves into the Atlantic coast states and the previously mentioned low pressure moves further out into the Atlantic. Trough the remainder of the week, the high will move off the coast lagging a weakening ridge across Florida. Local winds will slacken and veer further. Expect temperatures to slowly moderate back to near normal. Slight to chance probability of precipitation will be expected through this period as low level moisture increases.

A strong cold front will push through Keys waters today. Expect northerly winds to trend upwards today into tonight. A Small Craft Advisory is in effect for the western half of Keys waters. The advisory will likely be expanded to all waters tonight. While our eastern waters may lull some tomorrow, winds will continue trending upwards on our western waters. This is a consequence of a strong high pressure sliding into the eastern United States and some day time heating over the Florida Mainland. Nevertheless, the strongest winds are expected tomorrow night into Wednesday morning. Thereafter, the high will moves into the Atlantic states then out into the ocean. Winds will gradually slacken and veer east to southeast.

NOAA Key West FL Office: Watches - Warnings - Advisories
FL...None. GM...Small Craft Advisory GMZ033-034.